In the Universal Mobile Telecommunications Standard (UMTS) air interface, a base station communicates with User Equipment (UE) continuously. Therefore, unlike the Global System of Mobile communications (GSM) standard, there is no discrete time slot allowed for the UE to measure the strength of other frequency channels. However, the UMTS standard has defined periods in this continuous transmission where the transmitter and receiver within the UE are “powered down”. These gaps are defined as the compressed mode, and as such the UE has the opportunity of making measurements of the received signal strength on other frequency channels. It the received signal strength on a different channel is stronger, the UE changes channel as commanded by the network's Radio Resource Management (RRM) that is in control of the Radio Link This improves the quality of service to the UE. Additionally, this allows the UE to roam between broadcast cells.
During the compressed mode, the transmission of signals from the UE can be halted so as to reduce interference on the received channels that are being measured.
In a dual mode UE, both the UMTS standard and the GSM standard are supported. This means, during compressed mode, measurement of both the UMTS standard and the GSM standard received signals can be performed.
Accordingly, during compressed mode, the GSM measurement receiver switches on to begin taking the measurements of the other frequency channels. However, this means that if the UE switches the GSM measurement receiver on too early, i.e. before the UMTS transmitter is “powered down”, the GSM receiver may cause internal interference on the UMTS signal that is being transmitted, and therefore repeated data transmission may be required. Accordingly, this increases power consumption.
Additionally, if the measurements made by the GSM measurement receiver are carried out at the start of the compressed mode gap, if the UMTS transmitter is not fully powered down, interference can occur on the GSM measured signal, and therefore repeated measurements of the GSM signal may be required. This again increases power consumption within the UE.
It is therefore an object of the present invention to address these problems.